diff --git a/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerModelTests.cs b/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerModelTests.cs
new file mode 100644
index 000000000..b4ced6878
--- /dev/null
+++ b/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerModelTests.cs
@@ -0,0 +1,87 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Microsoft.Spark.ML.Feature;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+using Microsoft.Spark.UnitTest.TestUtils;
+using Xunit;
+
+namespace Microsoft.Spark.E2ETest.IpcTests.ML.Feature
+{
+    [Collection("Spark E2E Tests")]
+    public class StringIndexerModelTests : FeatureBaseTests<StringIndexerModel>
+    {
+        private readonly SparkSession _spark;
+
+        public StringIndexerModelTests(SparkFixture fixture) : base(fixture)
+        {
+            _spark = fixture.Spark;
+        }
+
+        /// <summary>
+        /// Create a <see cref="DataFrame"/>, create a <see cref="StringIndexerModel"/> and test the
+        /// available methods.
+        /// </summary>
+        [Fact]
+        public void TestStringIndexerModel()
+        {
+            DataFrame input = _spark.CreateDataFrame(
+                new List<GenericRow>
+                {
+                new GenericRow(new object[] {0, "a"}),
+                new GenericRow(new object[] {1, "b"}),
+                new GenericRow(new object[] {2, "c"}),
+                new GenericRow(new object[] {3, "a"}),
+                new GenericRow(new object[] {4, "a"}),
+                new GenericRow(new object[] {5, "c"})
+                },
+                new StructType(new List<StructField>
+                {
+                    new StructField("id", new IntegerType()),
+                    new StructField("category", new StringType())
+                }));
+
+            string expectedUid = "theUid";
+            StringIndexer stringIndexer = new StringIndexer(expectedUid)
+                .SetInputCol("category")
+                .SetOutputCol("categoryIndex");
+
+            StringIndexerModel stringIndexerModel = stringIndexer.Fit(input);
+            DataFrame transformedDF = stringIndexerModel.Transform(input);
+            List<Row> observed = transformedDF.Select("category", new string[] { "categoryIndex" })
+                .Collect().ToList();
+            List<Row> expected = new List<Row>
+            {
+                new Row(new GenericRow(new object[] {"a", "0"})),
+                new Row(new GenericRow(new object[] {"b", "2"})),
+                new Row(new GenericRow(new object[] {"c", "1"})),
+                new Row(new GenericRow(new object[] {"a", "0"})),
+                new Row(new GenericRow(new object[] {"a", "0"})),
+                new Row(new GenericRow(new object[] {"c", "1"}))
+            };
+
+            observed.ForEach(a =>
+            {
+                Assert.Equal(a, expected.Where(b => b == a).FirstOrDefault());
+            }
+            );
+            Assert.Equal("category", stringIndexer.GetInputCol());
+            Assert.Equal("categoryIndex", stringIndexer.GetOutputCol());
+            Assert.Equal(expectedUid, stringIndexer.Uid());
+
+            using (var tempDirectory = new TemporaryDirectory())
+            {
+                string savePath = Path.Join(tempDirectory.Path, "stringIndexerModel");
+                stringIndexerModel.Save(savePath);
+
+                StringIndexerModel loadedModel = StringIndexerModel.Load(savePath);
+                Assert.Equal(stringIndexerModel.Uid(), loadedModel.Uid());
+            }
+        }
+    }
+}
diff --git a/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerTests.cs b/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerTests.cs
new file mode 100644
index 000000000..8fc2b70f7
--- /dev/null
+++ b/src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/StringIndexerTests.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Microsoft.Spark.ML.Feature;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+using Microsoft.Spark.UnitTest.TestUtils;
+using Xunit;
+
+namespace Microsoft.Spark.E2ETest.IpcTests.ML.Feature
+{
+    [Collection("Spark E2E Tests")]
+    public class StringIndexerTests : FeatureBaseTests<StringIndexer>
+    {
+        private readonly SparkSession _spark;
+
+        public StringIndexerTests(SparkFixture fixture) : base(fixture)
+        {
+            _spark = fixture.Spark;
+        }
+
+        /// <summary>
+        /// Create a <see cref="DataFrame"/>, create a <see cref="StringIndexer"/> and test the
+        /// available methods.
+        /// </summary>
+        [Fact]
+        public void TestStringIndexer()
+        {
+            string expectedUid = "theUid";
+            StringIndexer stringIndexer = new StringIndexer(expectedUid)
+                .SetInputCol("category")
+                .SetOutputCol("categoryIndex");
+
+            Assert.Equal("category", stringIndexer.GetInputCol());
+            Assert.Equal("categoryIndex", stringIndexer.GetOutputCol());
+            Assert.Equal(expectedUid, stringIndexer.Uid());
+
+            using (var tempDirectory = new TemporaryDirectory())
+            {
+                string savePath = Path.Join(tempDirectory.Path, "stringIndexer");
+                stringIndexer.Save(savePath);
+
+                StringIndexer loadedstringIndexer = StringIndexer.Load(savePath);
+                Assert.Equal(stringIndexer.Uid(), loadedstringIndexer.Uid());
+            }
+        }
+    }
+}
diff --git a/src/csharp/Microsoft.Spark/ML/Feature/StringIndexer.cs b/src/csharp/Microsoft.Spark/ML/Feature/StringIndexer.cs
new file mode 100644
index 000000000..d5bbab383
--- /dev/null
+++ b/src/csharp/Microsoft.Spark/ML/Feature/StringIndexer.cs
@@ -0,0 +1,174 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Spark.Interop;
+using Microsoft.Spark.Interop.Ipc;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+
+namespace Microsoft.Spark.ML.Feature
+{
+    /// <summary>
+    /// <see cref="StringIndexer"/> encodes a string column of labels to a column of label indices.
+    /// </summary>
+    public class StringIndexer : FeatureBase<StringIndexer>, IJvmObjectReferenceProvider
+    {
+        private static readonly string s_StringIndexerClassName =
+            "org.apache.spark.ml.feature.StringIndexer";
+
+        /// <summary>
+        /// Create a <see cref="StringIndexer"/> without any parameters.
+        /// </summary>
+        public StringIndexer() : base(s_StringIndexerClassName)
+        {
+        }
+
+        /// <summary>
+        /// Create a <see cref="StringIndexer"/> with a UID that is used to give the
+        /// <see cref="StringIndexer"/> a unique ID.
+        /// </summary>
+        /// <param name="uid">An immutable unique ID for the object and its derivatives.</param>
+        public StringIndexer(string uid) : base(s_StringIndexerClassName, uid)
+        {
+        }
+
+        internal StringIndexer(JvmObjectReference jvmObject) : base(jvmObject)
+        {
+        }
+
+        JvmObjectReference IJvmObjectReferenceProvider.Reference => _jvmObject;
+
+        /// <summary>
+        /// Executes the <see cref="StringIndexer"/> and transforms the schema.
+        /// </summary>
+        /// <param name="value">The Schema to be transformed</param>
+        /// <returns>
+        /// New <see cref="StructType"/> object with the schema <see cref="StructType"/> transformed.
+        /// </returns>
+        public StructType TransformSchema(StructType value) =>
+            new StructType(
+                (JvmObjectReference)_jvmObject.Invoke(
+                    "transformSchema",
+                    DataType.FromJson(_jvmObject.Jvm, value.Json)));
+
+        /// <summary>
+        /// Executes the <see cref="StringIndexer"/> and fits a model to the input data.
+        /// </summary>
+        /// <param name="source">The <see cref="DataFrame"/> to fit the model to.</param>
+        /// <returns><see cref="StringIndexerModel"/></returns>
+        public StringIndexerModel Fit(DataFrame source) =>
+            new StringIndexerModel((JvmObjectReference)_jvmObject.Invoke("fit", source));
+
+        /// <summary>
+        /// Gets the HandleInvalid.
+        /// </summary>
+        /// <returns>Handle Invalid option</returns>
+        public string GetHandleInvalid() => (string)_jvmObject.Invoke("getHandleInvalid");
+
+        /// <summary>
+        /// Sets the Handle Invalid option to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="handleInvalid">Handle Invalid option</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the Handle Invalid set.
+        /// </returns>
+        public StringIndexer SetHandleInvalid(string handleInvalid) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setHandleInvalid", handleInvalid));
+
+        /// <summary>
+        /// Gets the InputCol.
+        /// </summary>
+        /// <returns>Input Col option</returns>
+        public string GetInputCol() => (string)_jvmObject.Invoke("getInputCol");
+
+        /// <summary>
+        /// Sets the Input Col option to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="inputCol">Input Col option</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the Input Col set.
+        /// </returns>
+        public StringIndexer SetInputCol(string inputCol) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setInputCol", inputCol));
+
+        /// <summary>
+        /// Gets the InputCols array.
+        /// </summary>
+        /// <returns>Input Cols array option</returns>
+        public string[] GetInputCols() => (string[])_jvmObject.Invoke("getInputCols");
+
+        /// <summary>
+        /// Sets the Input Cols array option to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="inputCols">Input Cols array option</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the Input Cols array set.
+        /// </returns>
+        public StringIndexer SetInputCols(string[] inputCols) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setInputCols", inputCols));
+
+        /// <summary>
+        /// Gets the OutputCol.
+        /// </summary>
+        /// <returns>Output Col option</returns>
+        public string GetOutputCol() => (string)_jvmObject.Invoke("getOutputCol");
+
+        /// <summary>
+        /// Sets the Output Col option to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="outputCol">Output Col option</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the Output Col set.
+        /// </returns>
+        public StringIndexer SetOutputCol(string outputCol) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setOutputCol", outputCol));
+
+        /// <summary>
+        /// Gets the OutputCols array.
+        /// </summary>
+        /// <returns>Output Cols array option</returns>
+        public string[] GetOutputCols() => (string[])_jvmObject.Invoke("getOutputCols");
+
+        /// <summary>
+        /// Sets the Output Cols array option to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="outputCols">Output Cols array option</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the Output Cols array set.
+        /// </returns>
+        public StringIndexer SetOutputCols(string[] outputCols) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setOutputCol", outputCols));
+
+        /// <summary>
+        /// Gets the String Order Type.
+        /// </summary>
+        /// <returns>String Order Type</returns>
+        public string GetStringOrderType() => (string)_jvmObject.Invoke("getStringOrderType");
+
+        /// <summary>
+        /// Sets the String Order Type to <see cref="StringIndexer"/>.
+        /// </summary>
+        /// <param name="stringOrderType">String Order Type</param>
+        /// <returns>
+        /// <see cref="StringIndexer"/> with the String Order Type set.
+        /// </returns>
+        public StringIndexer SetStringOrderType(string stringOrderType) =>
+            WrapAsStringIndexer((JvmObjectReference)_jvmObject.Invoke("setStringOrderType", stringOrderType));
+
+        /// <summary>
+        /// Loads the <see cref="StringIndexer"/> that was previously saved using Save.
+        /// </summary>
+        /// <param name="path">The path the previous <see cref="StringIndexer"/> was saved to</param>
+        /// <returns>New <see cref="StringIndexer"/> object, loaded from path</returns>
+        public static StringIndexer Load(string path) =>
+            WrapAsStringIndexer(
+                SparkEnvironment.JvmBridge.CallStaticJavaMethod(
+                    s_StringIndexerClassName,
+                    "load",
+                    path));
+
+        private static StringIndexer WrapAsStringIndexer(object obj) =>
+            new StringIndexer((JvmObjectReference)obj);
+    }
+}
diff --git a/src/csharp/Microsoft.Spark/ML/Feature/StringIndexerModel.cs b/src/csharp/Microsoft.Spark/ML/Feature/StringIndexerModel.cs
new file mode 100644
index 000000000..e16757a93
--- /dev/null
+++ b/src/csharp/Microsoft.Spark/ML/Feature/StringIndexerModel.cs
@@ -0,0 +1,92 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using Microsoft.Spark.Interop;
+using Microsoft.Spark.Interop.Ipc;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+
+namespace Microsoft.Spark.ML.Feature
+{
+    public class StringIndexerModel
+        : FeatureBase<StringIndexerModel>, IJvmObjectReferenceProvider
+    {
+        private static readonly string s_stringIndexerModelClassName =
+            "org.apache.spark.ml.feature.StringIndexerModel";
+
+        /// <summary>
+        /// Creates a <see cref="StringIndexerModel"/> without any parameters
+        /// </summary>
+        /// <param name="vocabulary">The vocabulary to use</param>
+        public StringIndexerModel(List<string> vocabulary)
+            : this(SparkEnvironment.JvmBridge.CallConstructor(
+                s_stringIndexerModelClassName, vocabulary))
+        {
+        }
+
+        /// <summary>
+        /// Creates a <see cref="StringIndexerModel"/> with a UID that is used to give the
+        /// <see cref="StringIndexerModel"/> a unique ID
+        /// </summary>
+        /// <param name="uid">An immutable unique ID for the object and its derivatives.</param>
+        /// <param name="vocabulary">The vocabulary to use</param>
+        public StringIndexerModel(string uid, List<string> vocabulary)
+            : this(SparkEnvironment.JvmBridge.CallConstructor(
+                s_stringIndexerModelClassName, uid, vocabulary))
+        {
+        }
+
+        internal StringIndexerModel(JvmObjectReference jvmObject) : base(jvmObject)
+        {
+        }
+
+        JvmObjectReference IJvmObjectReferenceProvider.Reference => _jvmObject;
+
+        /// <summary>
+        /// Loads the <see cref="StringIndexerModel"/> that was previously saved using Save
+        /// </summary>
+        /// <param name="path">
+        /// The path the previous <see cref="StringIndexerModel"/> was saved to
+        /// </param>
+        /// <returns>New <see cref="StringIndexerModel"/> object</returns>
+        public static StringIndexerModel Load(string path) =>
+            WrapAsStringIndexerModel(
+                SparkEnvironment.JvmBridge.CallStaticJavaMethod(
+                    s_stringIndexerModelClassName, "load", path));
+
+        /// <summary>
+        /// Check transform validity and derive the output schema from the input schema.
+        /// 
+        /// This checks for validity of interactions between parameters during Transform and
+        /// raises an exception if any parameter value is invalid.
+        ///
+        /// Typical implementation should first conduct verification on schema change and parameter
+        /// validity, including complex parameter interaction checks.
+        /// </summary>
+        /// <param name="value">
+        /// The <see cref="StructType"/> of the <see cref="DataFrame"/> which will be transformed.
+        /// </param>
+        /// <returns>
+        /// The <see cref="StructType"/> of the output schema that would have been derived from the
+        /// input schema, if Transform had been called.
+        /// </returns>
+        public StructType TransformSchema(StructType value) =>
+            new StructType(
+                (JvmObjectReference)_jvmObject.Invoke(
+                    "transformSchema",
+                    DataType.FromJson(_jvmObject.Jvm, value.Json)));
+
+        /// <summary>
+        /// Converts a DataFrame with a text document to a sparse vector of token counts.
+        /// </summary>
+        /// <param name="document"><see cref="DataFrame"/> to transform</param>
+        /// <returns><see cref="DataFrame"/> containing the original data and the counts</returns>
+        public DataFrame Transform(DataFrame document) =>
+            new DataFrame((JvmObjectReference)_jvmObject.Invoke("transform", document));
+
+        private static StringIndexerModel WrapAsStringIndexerModel(object obj) =>
+            new StringIndexerModel((JvmObjectReference)obj);
+    }
+}